Collaborative Software Debugging In A Distributed System With Private Debug Sessions

ABSTRACT

In a distributed system that includes a debug server and debug clients coupled for data communications through a data communications network, where the debug server includes a debug administrator, a message router, a back-end debugger, and a debuggee, collaborative software debugging includes receiving, by the debug server from the debug clients, application-level messages including receiving, from a requesting debug client, a request to establish a private debug session of the debuggee; routing, by the message router, the application-level messages among the debug clients, the debug administrator, and the back-end debugger, including forwarding, to the back-end debugger, the request to establish a private debug session of the debuggee; and; and returning, by the debug server to the debug clients in response to the application-level messages routed to the back-end debugger, client-specific debug results, including establishing the private debug session of the debuggee for the requesting debug client.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention is data processing, or, more specifically, methods, apparatus, and products for collaborative software debugging in a distributed system.

2. Description of Related Art

Software source code is increasingly complex and is often developed by various developers, sometimes physically dispersed from one another. One part of software development, source code debugging, is especially complex in today's distributed software development environments. In debugging, it is often useful for two or more developers to work together in real-time to debug the source code. Further, during such debugging, developers may have differing interests in different portions of the source code. At present, there are no debug engines available that enable remotely distributed developers to debug the same source code collaboratively in real-time, while separately viewing different results of the same debugging.

SUMMARY OF THE INVENTION

Methods, apparatus, and products for collaborative software debugging in a distributed system are disclosed. In embodiments of the present invention, the distributed system includes a debug server, a plurality of debug clients, and a data communications network. The debug server is coupled for data communications to the plurality of debug clients through the data communications network and the debug server includes a debug administrator, a message router, a back-end debugger, and a debuggee. From the perspective of the debug server, collaborative software debugging in the distributed system includes: receiving, by the debug server from the debug clients asynchronously during a debug session of the debuggee, a plurality of application-level messages, including receiving, from a requesting debug client, a request to establish a private debug session of the debuggee; routing, by the message router in accordance with an application-level message passing protocol, the application-level messages among the debug clients, the debug administrator, and the back-end debugger, thereby providing distributed control of the back-end debugger to the debug clients with application-level messages routed to the back-end debugger, including forwarding, to the back-end debugger, the request to establish a private debug session of the debuggee; and returning, by the debug server to the debug clients in response to the application-level messages routed to the back-end debugger, client-specific debug results, including establishing the private debug session of the debuggee for the requesting debug client.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descriptions of exemplary embodiments of the invention as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 sets forth a network diagram of a distributed system in which collaborative software debugging is carried out according to embodiments of the present invention.

FIG. 2 sets forth an example client-specific graphical user interface (GUI) presented to a user of a debug client in accordance with embodiments of the present invention.

FIG. 3 sets forth a flowchart illustrating an exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention.

FIG. 4 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to join a debug session.

FIG. 5 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to leave a debug session.

FIG. 6 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to distribute data to other debug clients.

FIG. 7 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to issue a command to the back-end debugger.

FIG. 8 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to establish an event notification with the back-end debugger.

FIG. 9 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to register a group of debug clients.

FIG. 10 sets forth a flowchart illustrating a further exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention.

FIG. 11 sets forth a flowchart illustrating a further exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention.

FIG. 12 sets forth a flowchart illustrating a further exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention.

FIG. 13 sets forth a flowchart illustrating a further exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary methods, apparatus, and products for collaborative software debugging in a distributed system in accordance with the present invention are described with reference to the accompanying drawings, beginning with FIG. 1. FIG. 1 sets forth a network diagram of a distributed system in which collaborative software debugging is carried out according to embodiments of the present invention. The term ‘debug,’ and its variations—debugged, debugging, and so on—as used in this specification generally refers to a methodical process of finding and reducing the number of bugs, or defects, in a computer program, that is, in source code of the computer program. Debugging may also be carried out to produce other results—decrease source code size, increase efficiency of the source code, decrease memory use by the executed source code, and so on as will occur to readers of skill in the art. The source code of a software program or application being debugged is referred to in this specification as a ‘debuggee.’

The system of FIG. 1 is a distributed system. The term ‘distributed’ generally describes a system in which elements of the system are coupled for data communications through a data communications network, in many cases, a loosely-coupled data communications network. The distributed system of FIG. 1, for example, includes a debug server (102), a plurality of debug clients (104), and a data communications network (100). The debug server (102) in the example distributed system of FIG. 1 is coupled for data communications to the plurality of debug clients (104) through the data communications network (100). The term ‘distributed’ may also refer, as context requires, to the physical distribution of the debug clients (104). That is, each debug client (106, 108, 110, and 112) may physically remote from each of the other debug clients. Clients (106 and 108) may be located in different states in the United States, while client (110) may be located in China, and client (112) may be located in Japan. The plurality of clients (104) is ‘distributed’ physically in various locations.

In the distributed system of FIG. 1, each of the debug clients (106, 108, 110, and 112) and the debug server (102) is implemented as automated computing machinery, a computer. For clarity of explanation, not limitation, the components comprising the debug server (102) are similar to and bear the same numbers as corresponding components comprising each of the debug clients (104). Similar components may be described below with respect to only one of the debug server (102) or a debug client, but such descriptions applies to components of both the debug server and the debug client.

Each of the debug clients (106, 108, 110, 112) of FIG. 1 includes at least one computer processor (156) or ‘CPU’ as well as random access memory (168) (‘RAM’) which is connected through a high speed memory bus (166) and bus adapter (158) to processor (156) and to other components of the debug clients (106, 108, 110, 112). The debug server (102) includes similar components coupled in similar ways.

Stored in RAM (168) of each debug client (106, 108, 110, 112) is a client debug application (128), a module of computer program instructions that, when executed by the computer processor (156) of the debug client, causes the debug client to carry out client-side collaborative software debugging in accordance with embodiments of the present invention. The client debug application (128) of each debug client, say client (106) as an example, carries out client-side collaborative software debugging in accordance with embodiments of the present invention by: presenting, by the debug client (106) to a user (not shown) of the debug client (106), a client-specific GUI (124). In the example of FIG. 1, the client-specific GUI (124) is a client-specific display of a debug session of the debuggee. The phrase ‘client-specific’ as used here describes a GUI and display of a debug session that may differ from other debug clients' GUI and display of the same debug session. A debug session is a semi-permanent interactive information interchange between at least one debug client and a debug server for the purposes of a debugging a particular debuggee. A session is set up or established at a certain point in time, and torn down at a later point in time. An established communication session may involve more than one message in each direction.

The client debug application (128) of the debug client (106) may also detect user input through the client-specific GUI, generate, in dependence upon the detected user (100) input, one or more application-level messages (126), and send the application-level messages to the debug server (102). The phrase ‘application-level’ is used to describe messages that have meaning at a particular level in a data communications protocol model or framework. Consider, as one example of a data communications protocol model, the Open Systems Interconnection model that has seven layers, the application layer being the ‘highest’ and the physical layer being the lowest. Consider also, as another example, the TCP/IP model, which sets forth the application layer at the highest level and a link layer at the lowest level. The relative terms—higher and lower—describe a protocol's ‘closeness’ with regard to physical hardware (cables and the like) upon which data communications are passed. Each higher layer is a greater level of abstraction. In both models, the application layer or application-level is the highest level, farthest away from hardware and most abstracted layer. In the examples provided here, the application-level messages are abstracted from the data communications protocols used to transmit the data making up the application-level messages across one or many physical connections.

Stored in RAM (168) of the debug server (102) is a listening agent (129), a module of computer program instructions that listens on a port for debug client requests where that port is well-known to the client. The term ‘server’ may, as context requires, refer to either or both of a server application or a computer upon which such a server application is executing. For clarity, the debug server (102) in the example of FIG. 1 is depicted and described as a computer upon which a server application executes. The listening agent (129) may also provide debug clients with a list of available collaborative debug server applications (130) or begin execution of a particular collaborative debug server application (130) upon request. A debug client, for example, may request that a particular type of collaborative debug server application be started for debugging a particular debuggee. The server (102) in the example of FIG. 1, may support simultaneous execution of several different debug server applications, each of which may debug separate debuggees. The listening agent may also provide to a requesting debug client, a port, socket, or other data communications identifier of the collaborative debug server application with which the requesting debug client is to communicate with during a debug session. That is, the listening agent (129) effectively brokers communications between a collaborative debug server application (130) and a debug client (104).

Also stored in RAM (168) of the debug server (102) is a collaborative debug server application (130), a module of computer program instructions that, when executed by the computer processor (156) of the debug server, causes the debug server (102) to carry out server-side collaborative software debugging in accordance with embodiments of the present invention. The collaborative debug server application (130) also includes a debug administrator (114), a message router (116), a back-end debugger (118), and a debuggee (120).

The debug administrator (114) is a module of computer program instructions that administers a collaborative debug session, administering client identifiers, registering and unregistering clients in a debug session, and so on. A back-end debugger (118) is an application that controls operation of another application—the debuggee (120)—for the purpose of testing execution of the debuggee. The source code of the debuggee may run on an instruction set simulator (ISS), a technique that allows great power in its ability to halt when specific conditions are encountered but which will typically be somewhat slower than executing the code directly on a processor for which the code is written. When execution of a program crashes or reaches a preset condition, a debugger typically displays the position in the source code at which the execution of the program crashed. A ‘crash’ occurs when the program cannot normally continue because of a programming bug. In addition to displaying a position in source code when execution of the source code crashes, debuggers also often offer other functions such as running a program step by step (single-stepping or program animation), stopping, breaking, or pausing the program to examine the current state, at some event or specified instruction by means of a breakpoint, and tracking the values of some variables.

The term ‘back-end’ is used here to indicate that the debugger (118) in the example of FIG. 1 is indirectly controlled by multiple clients. As explained below in detail, the back-end debugger (118) is controlled indirectly by multiple clients through use of an intermediary—the message router (116). From the perspective of the back-end debugger (118), the debugger is controlled by a single source, the message router (116). The message router, however, operates as intermediary between multiple debug clients and the debugger. The term ‘back-end’ may be further described by contrast to the term ‘front-end.’ Debugger front-ends are popular extensions to debugger engines that provide Integrated Development Environment (‘IDE’) integration, program animation, and visualization features, rather than console-based command line interfaces. The ‘front-end’ directly faces a client, in contrast to the ‘back-end’ debugger (118) in the example of FIG. 1, which interfaces indirectly with the clients through the message router (116).

The collaborative debug server application (130) carries out server-side collaborative software debugging in accordance with embodiments of the present invention by: receiving, by the debug server (102) from the debug clients (104) asynchronously during a debug session of the debuggee (120), a plurality of application-level messages (126); routing, by the message router (116) in accordance with an application-level message passing protocol, the application-level messages (126) among the debug clients, the debug administrator, and the back-end debugger. In routing the messages in the example of FIG. 1, the message router (116) provides distributed control of the back-end debugger (118) to the debug clients (104) with the application-level messages (126) routed to the back-end debugger (118). The debug server application (138) also returns, to the debug clients (104) in response to the application-level messages routed to the back-end debugger, client-specific debug results. Each debug client (106, 108, 110, 112), is also configured to receive the client-specific debug results as application-level reply messages (126) and display, in the client-specific GUI (180), the client-specific debug results.

The example debug server (102) is also configured to receive, from a requesting debug client—such as debug client (106), for example—a request (127) to establish a private debug session of the debuggee (120). A private debug session, as the term is used in this specification, refers to a non-collaborative debug session formed from a collaborative debug session at the behest of a debug client. In effect, a private debug session is a copy of a collaborative debug session for operation and administration by a single debug client. Other debug clients need not be aware of the private debug session nor have any interaction or control of the private debug session. Establishment of the private debug session and control of the private debug session does not interrupt the collaborative debug session from the perspective of the collaborative debug clients. The private debug session enables a debug client to control debugging of the copy (120 a) of the debuggee from the same point—same line of code, function, breakpoint and so on—at which the collaborative debug session exists at the time the private debug session is established. A debug client may, for example, evaluate expressions, modify variable values, set breakpoints, and otherwise control debugging of the copy of the debuggee without affecting or interrupting the collaborative debug session. Consider, for example, that a user of a particular debug client desires testing the debuggee under a particular set of circumstances, such as setting a variable's value to zero. Rather than performing this test in the collaborative debug session, requiring all collaborative debug clients to participate or endure the test, the particular debug client may request that a private debug session be established, set the variable's value to zero in the private debug sessions and begin testing the debuggee in the private debug session—without interrupting the collaborative debug session.

Upon receipt of the request (127) to establish the private debug session, the message router (116) of the debug server (102) forwards, to the back-end debugger (118), the request (127) to establish a private debug session of the debuggee and the back-end debugger establishes the private debug session of the debuggee for the requesting debug client.

Also stored RAM (168) of the debug server (102) and debug clients (104) is an operating system (154). An operating system is a computer software component that is responsible for execution of application programs and for administration of access to computer resources, memory, processor time, and I/O functions, on behalf of application programs. Operating systems useful in computers of a distributed system in which collaborative software debugging is carried out according to embodiments of the present invention include UNIX™, Linux™, Microsoft XP™, AIX™, IBM's i5/OS™, and others as will occur to those of skill in the art. The operating system (154), collaborative debug server application (130), debuggee (120), client debug application (128), client-specific debug GUI (124), and so on in the example of FIG. 1 are shown in RAM (168), but many components of such software typically are stored in non-volatile memory also, such as, for example, on a disk drive (170).

Each of the debug server (102) and debug clients (104) of FIG. 1 includes disk drive adapter (172) coupled through expansion bus (160) and bus adapter (158) to processor (156) and other components of the debug server (102) and debug clients (104). Disk drive adapter (172) connects non-volatile data storage to each of the debug server (102) and debug clients (104) in the form of disk drive (170). Disk drive adapters useful in computers that provide collaborative software debugging according to embodiments of the present invention include Integrated Drive Electronics (‘IDE’) adapters, Small Computer System Interface (‘SCSI’) adapters, and others as will occur to those of skill in the art. Non-volatile computer memory also may be implemented for as an optical disk drive, electrically erasable programmable read-only memory (so-called ‘EEPROM’ or ‘Flash’ memory), RAM drives, and so on, as will occur to those of skill in the art.

Each of the example debug server (102) and debug clients (104) of FIG. 1 includes one or more input/output (‘I/O’) adapters (178). I/O adapters implement user-oriented input/output through, for example, software drivers and computer hardware for controlling output to display devices such as computer display screens, as well as user input from user input devices (181) such as keyboards and mice. Each of the example debug server (102) and debug clients (104) of FIG. 1 includes a video adapter (209), which is an example of an I/O adapter specially designed for graphic output to a display device (180) such as a display screen or computer monitor. Video adapter (209) is connected to processor (156) through a high speed video bus (164), bus adapter (158), and the front side bus (162), which is also a high speed bus.

Each of the example debug server (102) and debug clients (104) of FIG. 1 includes a communications adapter (167) for data communications with other computers and for data communications with a data communications network (100). Such data communications may be carried out serially through RS-232 connections, through external buses such as a Universal Serial Bus (‘USB’), through data communications networks such as IP data communications networks, and in other ways as will occur to those of skill in the art. Communications adapters implement the hardware level of data communications through which one computer sends data communications to another computer, directly or through a data communications network. Examples of communications adapters useful in computers that provide collaborative software debugging according to embodiments of the present invention include modems for wired dial-up communications, Ethernet (IEEE 802.3) adapters for wired data communications network communications, and 802.11 adapters for wireless data communications network communications.

The arrangement of debug servers, debug clients, data communications networks, and other devices making up the exemplary system illustrated in FIG. 1 are for explanation, not for limitation. Data processing systems useful according to various embodiments of the present invention may include additional servers, routers, other devices, and peer-to-peer architectures, not shown in FIG. 1, as will occur to those of skill in the art. Networks in such data processing systems may support many data communications protocols, including for example TCP (Transmission Control Protocol), IP (Internet Protocol), HTTP (HyperText Transfer Protocol), WAP (Wireless Access Protocol), HDTP (Handheld Device Transport Protocol), and others as will occur to those of skill in the art. Various embodiments of the present invention may be implemented on a variety of hardware platforms in addition to those illustrated in FIG. 1.

For further explanation, FIG. 2 sets forth an example client-specific GIU presented to a user of a debug client in accordance with embodiments of the present invention. The example GUI (124) of FIG. 2 provides an interface for a user of a debug client to effectively control, collaboratively with other client debuggers, the back-end debugger of a debug server. The example GUI (124) of FIG. 2 includes a menu bar (208), including a number of separate menus: a File menu, an Edit menu, a View menu, a Collaborate menu, and a Help menu. The Collaborate menu (206), when selected, may provide a user with various menu items that support collaborative debugging. The debug GUI of each debug client in a distributed system for which collaborative software debugging is carried out in accordance with embodiments of the present invention is client-specific, meaning any one debug GUI may be configured differently, displayed differently, or operate differently, than any other debug client's GUI, while all debug clients collaboratively control the same, single back-end debugger of a debug server during the same debug session of the same debuggee. One debug GUI may display the source code at one location (line number) while another debug GUI displays the source code at another location; one debug GUI displays a call stack of one thread, while another debug GUI displays a call stack of another thread; one debug GUI displays evaluation results of one variable, while another debug GUI displays evaluation results of another variable; and so on as will occur to readers of skill in the art. The example client-specific debug GUI (124) of FIG. 2 provides a client-specific display of debugging along with collaborative, or ‘distributed,’ control of the debugger, rather than all debug clients displaying only the same GUI as a single master debug client, where the master client has absolute, not collaborative, control over the debugger until passing that control to another client.

The example GUI (124) of FIG. 2 also includes several independent portions—called panes (as in ‘window panes’) for clarity of explanation—a project pane (202), a source code pane (210), and two separate data panes (204, 212). Project pane (202) presents the files and resources available in a particular software development project. Source code pane (210) presents the source code of debuggee. The data panes (204, 212) present various data useful in debugging the source code. In the example of FIG. 2, data pane (204) includes three tabs, each of which presents different data: a call stack tab (214), a register tab (214), and a memory tab (218). Data pane (212) includes four tabs: a watch list tab (220), a breakpoints (222) tab, a local variable tab (224), and a global variable tab (226).

The example GUI (124) of FIG. 2 also supports private debug session establishment. In the menu bar (208) of the example GUI (124) of FIG. 2 is a GUI button (207) for creating a private session. Upon invocation of the GUI button (207) the GUI (124) generates and sends to the debug server, in one or more application-level messages, a request to establish a private debug session. Once established, the debug client presenting the example GUI (124) of FIG. 2 may also present a separate GUI for the private debug session or, as in the example of FIG. 2, present the private debug session in the a separate tabbed window. In the example of FIG. 2, the GUI (124) includes a tab for the collaborative session, session::1 (230), and the private debug session, Session::2 (232). Immediately after the private debug session is established, the display in the Session::2 tab (232) will match the display of the Session::1 tab (230), assuming no changes have occurred in the collaborative debug session. Any operation by the debug client two the private debug session will not interrupt or affect the operation of the collaborative debug session.

The GUI items, menus, window panes, tabs, and so on depicted in the example client-specific GUI (124) of FIG. 2, are for explanation, not for limitation. Other GUI items, menu bar menus, drop-down menus, list-boxes, window panes, tabs, and so on as will occur to readers of skill in the art may be included in client-specific GUIs presented by debug clients in a distributed system in which collaborative software debugging is carried out in accordance with embodiments of the present invention.

For further explanation, FIG. 3 sets forth a flowchart illustrating an exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention. In the method of FIG. 3, the distributed system includes a debug server (102), a plurality of debug clients (104), and a data communications network (100 on FIG. 1). The debug server (102) is coupled for data communications to the plurality of debug clients (104) through the data communications network (100). The debug server (102) further includes a debug administrator (114), a message router (116), a back-end debugger (118), and a debuggee (120).

The method of FIG. 3 includes presenting (302), by each debug client (104) to a user (101 on FIG. 1) of the debug client (104), a client-specific GUI (124). In the method of FIG. 3, each debug client's (104) client-specific GUI (124) is implemented as a client-specific display of a debug session of the debuggee (120).

Presenting (302) a client-specific GUI (124) may be carried out by rendering the GUI (124) on a display device (180), with each debug client operating semi-independently from other debug clients in presenting the GUI (124). As mentioned above, each GUI (124) may be display different debugging attributes even though each of the debug clients presenting the GUI (124) are participating in the same debug session of the same debuggee.

The method of FIG. 3 also includes detecting (304), by each debug client (104), user (101 on FIG. 1) input (306) through the client-specific GUI (124). Detecting (304), user input (306) through the client-specific GUI (124) may be carried out in various ways including, for example, detecting mouse-overs, detecting keyboard keystrokes, detecting keyboard shortcuts, detecting explicit commands entered into a field presented to receive such commands, detecting selection of drop-down menu items, detecting mouse-clicks on GUI items, such as GUI buttons, and so on.

The method of FIG. 3 also includes generating (308), by each debug client (104) in dependence upon the detected user input (306), one or more application-level messages (310) and sending (312), by each debug client (104), the application-level messages (310) to the debug server (102). Generating (308) one or more application-level messages (310) may be carried out by identifying, from message generation rules, a message type, and creating application-level messages of the message type that includes at least an identification of a sender, a recipient, and the message type. Examples of message types are described below in detail and include a JOIN message type, a LEAVE message type, a DISTRIBUTE REQEUST message type, a COMMAND REQUEST message type, and EVENT REQUEST message type, a REGISTER GROUP message type, a CONFIRMATION REPLY message type, a REQUEST REPLY message type, and an EVENT REPLY message type.

The method of FIG. 3 also includes receiving (314), by the debug server (102) from the debug clients (104) asynchronously during a debug session of the debuggee (120), the application-level messages (310). Receiving (314) the application-level messages (310) may be carried out by listening on a well-known data communications socket, upon which application-level messages (310) of the kind sent by the debug clients (104) are expected to be received.

The method of FIG. 3 also includes routing (316), by the message router (116) in accordance with an application-level message passing protocol (311), the application-level messages (310) among the debug clients (104), the debug administrator (114), and the back-end debugger (118). In the method of FIG. 3, routing (316) the application-level messages (310) includes providing (318) distributed control of the back-end debugger (118) to the debug clients (104) with application-level messages (310) routed to the back-end debugger (118). That is, the messages routed to the back-end debugger—message received from any of the debug clients at any time during the debug session of the debuggee—control operation of the back-end debugger. The application-level messages control debugging of the debugging.

The method of FIG. 3 also includes returning (320), by the debug server (102) to the debug clients (104) in response to the application-level messages (310) routed to the back-end debugger (118), client-specific debug results (322). Returning (320), client-specific debug results (322) to the debug clients (104) may be carried out by generating, by the debug server or more specifically, the message router (116), one or more application-level messages forming a reply or replies that include the results and sending the replies to the debug clients via the data communications network (100 on FIG. 1).

The method of FIG. 3 also includes receiving (324), by each debug client (104) responsive to the application-level messages (310), client-specific debug results (322) and displaying (326), by each debug client in the client-specific GUI (124) on a display device (180), the client-specific debug results (322).

As described above, once received by a debug server (102) from a debug client, an application-level message (310) in the example of FIG. 3, the application-level message (310) is routed to one of a back-end debugger (118), a debug administrator (114), or one or more other debug clients (104) in dependence upon an application-level message passing protocol (311). For further explanation of such a message passing protocol useful in distributed systems in which collaborative software debugging is carried out in accordance with embodiments of the present invention, FIGS. 4-9 set forth various sequence diagrams that illustrate message passing in accordance with the message passing protocol. FIG. 4, therefore, sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to join a debug session. The method of FIG. 4 is carried out in a distributed system similar to the system of FIG. 1 which includes a debug server (102), a plurality of debug clients (104), and a data communications network (100 on FIG. 1). The debug server (102) is coupled for data communications to the plurality of debug clients (104) through the data communications network (100). The debug server (102) further includes a debug administrator (114), a message router (116), a back-end debugger (118 on FIG. 1), and a debuggee (120 on FIG. 1).

The method of FIG. 4, illustrated in a sequence diagram rather than a flowchart, is similar to the method of FIG. 3 in that the method of FIG. 4 depicts a debug client—the requesting client (402) of FIG. 4—generating (308 on FIG. 3) one or more application-level messages (310 on FIG. 3). In the example of FIG. 4, the requesting client (402) generates a request (406) to join the debug session. In the method of FIG. 4, the request is implemented as an application-level message having a JOIN REQUEST message type (408), an identification (410) of the sender of the request to join (such as an IP address, Socket Number, or port number), and an identification (412) of one or more intended recipients. Such intended recipients may include the sender, all other debug clients registered in the session, or some subset of debug clients registered in the session. As explained below in more detail, an identification of an intended recipient in the example request (406) to join is not an identification of a recipient of the request itself—the debug server (102) is the recipient of the request itself—instead, the identification of an intended recipient in the request join actually identifies a recipient of future replies to the request. The request (406) may also include a message identifier, uniquely identifying the request. Responses to the request may include such a message identifier so that debug clients may identify the request to which the response relates.

In the example of FIG. 4, sending (312 on FIG. 3), by the requesting client (402), the application-level messages (310 on FIG. 3) to the debug server (102), includes sending the request (406) to join the debug session and receiving (314 on FIG. 3) the application-level messages (310 on FIG. 3) includes receiving, by the debug server (102) and, more specifically, the message router (116), the request (406) to join the debug session.

The method of FIG. 4 also includes sending, by the message router to the requesting debug client (402), in response to receiving the request (406), a confirmation (414) of receipt of the request (406) to join, the confirmation implemented as an application-level message having a CONFIRMATION REPLY message type (416). The confirmation may also include a message identifier that uniquely identifies the request (406) for which the confirmation reply is confirming receipt. The requesting debug client (402) in the example of FIG. 4 receives the confirmation (414). If the requesting debug client (402) does not receive a confirmation (414) after a predefined amount of time, the requesting client (402) may resend the request (406).

After receiving the request (406), the message router (116) routes (316 on FIG. 3) the application-level messages by forwarding the request (406) to join the debug session to the debug administrator (114). The debug administrator (114) then registers the requesting debug client (402) in the debug session and assigns the requesting debug client (402) a client identifier (420) unique to the debug session. After assignment a client identifier may be used in message passing among the debug clients, debug server, and debug administrator to identify a recipient of a message, to identify a sender of a message, and so on. The debug administrator (114) may maintain a list, or other data structure, of available client identifiers and a table, or other data structure, of assigned client identifier. A table of assigned client identifiers may include a plurality of entries, with each entry representing a single client. Each entry in such a table may associate a client identifier with another identification of the client—a MAC (Media Access Control) address, an IP (Internet Protocol) address, a socket identifier, and so on as will occur to readers of skill in the art.

After assigning the client identifier (420), the debug administrator (114) may return, to the message router (116), the assigned client identifier (420) and the message router (116) may send the client identifier (420) along to the requesting client (402) in a reply (422) to the request (406) to join the debug session. In the example of FIG. 4, the reply (422) is implemented as an application-level message having a REQUEST REPLY message type (424), an indication (430) of future replies responsive to the request (406) to join, an identification (426) of sender of the reply, and a payload (432) that includes the assigned client identifier (420). In the method of FIG. 4, the requesting client (402) receives the reply (422).

In the method of FIG. 4, the message router (116) also sends, to debug clients (404) identified as intended recipients in the request (406) to join, an additional reply (434) to the request (406) to join and the debug clients (404) receive the additional reply (434). In the method of FIG. 4, the additional reply (434) is implemented as an application-level message having a REQUEST REPLY message type (436), an indication (442) of future replies responsive to the request to join, and a payload (444) that includes the assigned client identifier (420) and an indication that the requesting debug client is registered in the debug session.

For further explanation, FIG. 5 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to leave a debug session. The method of FIG. 5 is carried out in a distributed system similar to the system of FIG. 1 which includes a debug server (102), a plurality of debug clients (104), and a data communications network (100 on FIG. 1). The debug server (102) is coupled for data communications to the plurality of debug clients (104) through the data communications network (100). The debug server (102) further includes a debug administrator (114), a message router (116), a back-end debugger (118 on FIG. 1), and a debuggee (120 on FIG. 1).

The method of FIG. 5 includes generating, by a requesting debug client (502), a request (506) to leave the debug session and receiving the request (502) to leave the debug session by the message router (116). In the example of FIG. 5, the request (506) is implemented as an application-level message having a LEAVE REQUEST message type (508), a sender's identification (510), an identification (512) of one or more intended recipients, and a payload (513) to distribute to the intended recipients upon leaving the debug session.

The method of FIG. 5 continues by the message router (116) sending, to the requesting debug client (502), a confirmation of receipt of the request (506) to leave and receiving by the requesting debug client (502) the confirmation. The confirmation in the example of FIG. 5 may be implemented as an application-level message having a CONFIRMATION REPLY message type (516).

The method of FIG. 5 also includes by forwarding the request (506) to leave the debug session to the debug administrator, unregistering, by the debug administrator (114), the requesting debug client from the debug session, including unassigning the requesting debug client's (502) client identifier, and returning, to the message router (116) a completion notification (520).

The message router (116) in the example of FIG. 5 then sends, to debug clients (504) identified as intended recipients in the request (502) to leave, a reply (522) to the request to leave and receiving, by the debug clients (504) identified as intended recipients, the reply (522) to the request to leave. The reply (522) may be implemented as an application-level message having a REQUEST REPLY message type (524), an identification (526) of a sender of the message, an identification of the recipient of the message (528), an indication (530) of future replies responsive to the request (506) to leave, and as a payload (542) of the reply, the payload (513) included in the request (513) to leave.

For further explanation, FIG. 6 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to distribute data to other debug clients. The method of FIG. 6 is carried out in a distributed system similar to the system of FIG. 1 which includes a debug server (102), a plurality of debug clients (104), and a data communications network (100 on FIG. 1). The debug server (102) is coupled for data communications to the plurality of debug clients (104) through the data communications network (100). The debug server (102) further includes a debug administrator (114), a message router (116), a back-end debugger (118 on FIG. 1), and a debuggee (120 on FIG. 1).

The method of FIG. 6 includes generating, by a requesting debug client (602), a request (606) to distribute data (613) to debug clients registered in the debug session, sending, to the debug server, the request (606), and receiving, by the message router (116), the request (606). In the example of FIG. 6, the request (606) to distribute data may be implemented as an application-level message having a DISTRIBUTE REQUEST message type (608), an identification of a sender (610) of the message, an identification (612) of one or more intended recipients (604), and a payload that includes data (613) to distribute to the intended recipients.

Responsive to receiving the request (606), the message router (116) in the example of FIG. 6, sends, to the requesting debug client (602), a confirmation of receipt of the request (606) to distribute data and the requesting debug client (602) receives the confirmation (614). In the example of FIG. 6, the confirmation may be implemented as an application-level message having a CONFIRMATION REPLY message type (616).

The method of FIG. 6 continues by sending, by the message router (116) to debug clients identified as intended recipients (602) in the request (606) to distribute data, a reply (622) to the request (606) to distribute data, and receiving, by the debug clients identified as intended recipients (602), the reply (622). In the example of FIG. 6, the reply (622) may be implemented as an application-level message having a REQUEST REPLY message type (624), an identification of a sender of the message (626), an identification (628) of a recipient of each message, an indication (630) of future replies responsive to the request (606) to distribute data, and a payload (632). The payload (632) of the reply (622) includes the data to distribute originally included in the request (606). That is, the payload (632) of the reply (622) is the payload (613) included in the request (606) to distribute data.

FIG. 7 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to issue a command to the back-end debugger. The method of FIG. 7 is carried out in a distributed system similar to the system of FIG. 1 which includes a debug server (102), a plurality of debug clients (104), and a data communications network (100 on FIG. 1). The debug server (102) is coupled for data communications to the plurality of debug clients (104) through the data communications network (100). The debug server (102) further includes a debug administrator (114), a message router (116), a back-end debugger (118 on FIG. 1), and a debuggee (120 on FIG. 1).

The method of FIG. 7 includes generating, by a requesting debug client (702), a request (706) to issue a command (718) to the back-end debugger (118), sending the request (706) to the debug server (102), and receiving the request (722) by the message router (116). In the example of FIG. 7, the request (706) may be implemented as an application-level message having a COMMAND REQUEST message type (708), an identification (710) of a sender of the message, an identification (712) of one or more intended recipients of results of executing the command, and a payload (713). The payload (713) of the request (706) in the example of FIG. 7 includes the command to issue to the back-end debugger. The command may be a text command to be entered into a command line interface of the back-end debugger. Examples of commands which may be issued to a back-end debugger through a command line interface, may include: backtrace, step, next, until, continue, clear, help, info breakpoints, info watchpoints, info registers, info threads, and so on as will occur to readers of skill in the art. These are merely some of many possible commands which may be issued to a debugger.

The method of FIG. 7 continues by sending, by the message router (116) to the requesting debug client (702), a confirmation (714) of receipt of the request (706) to issue the command (718) and receiving the confirmation by the requesting debug client (702). In the example of FIG. 7, the confirmation (714) is implemented as an application-level message having a CONFIRMATION REPLY message type (716).

The method of FIG. 7 also includes routing the request (706) to the back-end debugger (118) by issuing the command (718) to the back-end debugger (118) by the message router (116). The method of FIG. 7 continues by the back-end debugger, executing the issued command (718). For some commands, executing the command (718) causes the back-end debugger (118) to initiate execution (719) of the debuggee, for debugging purposes, monitor the execution of the debuggee, and gather results (720) of the execution. For other commands, the command may be executed entirely by the back-end debugger without initiating execution of the debuggee.

After executing the issued command in the example of FIG. 7, the back-end debugger (118) returns to the message router (116) results (720) of the execution of the issued command, the message router receives the results (718). The nature of the results (720) of the execution depend upon the type of command (718) executed by the back-end debugger. A command to evaluate a variable for example, may return as little as an integer, while a command to step into execution of the debuggee may return significantly more information—variable values, register values, memory values, line number, source code file name, and thread number and so on. The results (720), once received by the requesting client (702) may be used to control the client-specific GUI, changing the information displayed on the GUI.

The message router (116) in the example of FIG. 7 sends, to each of the requesting debug client (702) and debug clients (704) identified as intended recipients in the request (706) to issue the command (718), a reply (722) to the request to issue the command and the debug clients (704) and requesting client (702) receive the reply (722). In the example of FIG. 7, the reply (722) may be implemented as an application-level message having a REQUEST REPLY message type (724), an identification (726) of a sender of the message, an identification (728) of a recipient of the message, an indication (730) of future replies responsive to the request (706) to issue the command, and a payload (732) that includes the results (720) of executing the issued command.

FIG. 8 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to establish an event notification with the back-end debugger. The method of FIG. 8 is carried out in a distributed system similar to the system of FIG. 1 which includes a debug server (102), a plurality of debug clients (104), and a data communications network (100 on FIG. 1). The debug server (102) is coupled for data communications to the plurality of debug clients (104) through the data communications network (100). The debug server (102) further includes a debug administrator (114), a message router (116), a back-end debugger (118 on FIG. 1), and a debuggee (120 on FIG. 1).

The method of FIG. 8 includes generating, by a requesting debug client (802), a request (806) to establish, with the back-end debugger, an event notification associated with a particular event during the debug session, sending, to the debug server (102), the request (806), and receiving, by the message router, the request (806). In the example of FIG. 8, the request (806) may be implemented as an application-level message having an EVENT REQUEST message type (806), an identification (810) of a sender of the message, an identification (812) of one or more intended recipients of notifications of the of the event, and a payload (813) that includes a command (818) to issue to the back-end debugger (118) to establish the event notification. An event is a predefined occurrence during execution of debuggee. Such an event may include encountering a breakpoint, a watchpoint, a catchpoint, or the like. A breakpoint is a specification of a source code location at which a debuggee will pause or stop execution. A watchpoint is a breakpoint configured to pause or stop execution of the debuggee when a value of a particular expression changes. A catchpoint is another type of breakpoint configured to pause or stop execution of the debuggee when a specified event occurs such as the throwing of an exception or a load of a library, and so on.

The method of FIG. 8 also includes sending, by the message router (116) to the requesting debug client, a confirmation (814) of receipt of the request (806) to establish the event notification and receiving, by the requesting client (802), the confirmation. In the example of FIG. 8, the confirmation may be implemented as an application-level message having a CONFIRMATION REPLY message type (816).

The method of FIG. 8 also includes routing the request (806) to the back-end debugger by issuing, to the back-end debugger, the command (818) to establish the event notification. The back-end debugger (118) in the example of FIG. 8 may then execute the issued command including establishing the event notification associated with the particular event and assigning the event notification an event identifier (819). Establishing a notification of such an event may, for example, include setting and enabling a breakpoint, watchpoint, or catchpoint at a particular location in the source code specified by the requesting debug client (802) in the request (806).

The method of FIG. 8 includes returning, by the back-end debugger (118) to the message router (116), the event identifier (819), sending, by the message router (116) to each of the requesting debug client (802) and debug clients (804) identified as intended recipients in the request (806) to establish the event notification, a reply (822) to the request to establish the event notification, and receiving the reply (822) by the requesting client (802) and the intended recipients (804). In the example of FIG. 8, the reply may be implemented as an application-level message having a REPLY REQUEST message type (824), a sender identification (826), a recipient identification (828), an indication of future replies (830), and a payload (832) that includes the event identifier (832) and optionally a description of the event notification.

The method of FIG. 8 also includes: executing (834) the debuggee (120) by the back-end debugger (118); encountering, during the debug session, the particular event (836) associated with the event notification; providing, by the back-end debugger (118) to the message router (116), information (838) describing the particular event and the event identifier (819); and receiving, by the message router from the back-end debugger, the information (838) describing the particular event and the event identifier (819).

The method of FIG. 8 continues with the message router (116) sending, to each of the requesting debug client (802) and debug clients (804) identified as intended recipients in the request (806) to establish the event notification, a reply (840) to the request to establish the event notification and receiving by the requesting client (802) and by the intended recipients (804), the reply (811). In the example of FIG. 8, the reply (811) to the request (806) to establish the event notification may be implemented as an application-level message having an EVENT REPLY message type (842), a sender identification (844), a recipient identification (846), an indication (848) of future replies responsive to the request establish the event notification, and a payload (850) that includes the information (838) describing the particular event and the event identifier (819).

FIG. 9 sets forth a sequence diagram illustrating a further exemplary method of collaborative software debugging in accordance with embodiments of the present invention in which a debug client requests to register a group of debug clients. Once a group of debug clients is registered, as explained below, a group identifier is assigned to the group. Rather than listing out multiple client identifiers application-level messages intended for multiple recipients, debug clients may use a group identifier instead. Group identifiers may also be used for privacy or security in debugging—associating a breakpoint, variable, or portion of source code, for example, with a group identifier of a particular group and providing access only to members of the particular group.

The method of FIG. 9 is carried out in a distributed system similar to the system of FIG. 1 which includes a debug server (102), a plurality of debug clients (104), and a data communications network (100 on FIG. 1). The debug server (102) is coupled for data communications to the plurality of debug clients (104) through the data communications network (100). The debug server (102) further includes a debug administrator (114), a message router (116), a back-end debugger (118 on FIG. 1), and a debuggee (120 on FIG. 1).

The method of FIG. 9 includes generating, by a requesting debug client (902), a request (906) to register a group of debug clients, sending the request (906) to the debug server (102), and receiving the request (906) by the message router (116). In the example of FIG. 9, the request (906) may be implemented as an application-level message having a GROUP REGISTER REQUEST message type (908), a sender identification (910), an identification (912) of one or more intended recipients, and a payload (913) that includes client identifiers of a plurality of debug clients to include in the group of debug clients.

The method of FIG. 9 also includes sending, by the message router (116) to the requesting debug client (902), a confirmation (914) of receipt of the request (906) to register the group and receiving the confirmation (914) by the requesting debug client (902). In the example of FIG. 9, the confirmation (914) may be implemented as an application-level message having a CONFIRMATION REPLY message type (916).

The method of FIG. 9 also includes routing the request (906) to the debug administrator (114) and registering, by the debug administrator (114), the group of debug clients, including assigning the group of debug clients a group identifier (920) unique within the debug session. In the method of FIG. 9, the debug administrator (114) returns the group identifier (920) to the message router (116).

The method of FIG. 9 continues by sending, by the message router (116) to each of the requesting debug client (902) and the debug clients identified as intended recipients (904) in the request (906) to register the group of debug clients, a reply (922) to the request (906) and receiving by the requesting debug client (902) and the intended recipients (904), the reply (922). In the example of FIG. 9, the reply (922) may be implemented as an application-level message having a REQUEST REPLY message type (924), a sender identification (926), a recipient identification (928), an indication (930) of future replies responsive to the request to register the group of debug clients, and a payload (932) that includes the assigned group identifier (920).

FIG. 10 sets forth a flowchart illustrating a further exemplary method of collaborative software debugging in a distributed system, such as the example system depicted in FIG. 1, in accordance with embodiments of the present invention. FIG. 10 is directed primarily to operation of the debug server, rather than the debug clients, in carrying out collaborative debugging in accordance with embodiments of the present invention. FIG. 10 is similar to the method of FIG. 3 in that the method of FIG. 10 includes receiving (314) a plurality of application-level messages, routing (316) the application-level messages, and returning (320) client-specific debug results.

The method of FIG. 10 differs from the method of FIG. 3, however, in that in the method of FIG. 10, receiving (314) a plurality of application-level messages includes receiving (1002), from a requesting debug client, a request to establish a private debug session of the debuggee. Receiving (1002) a request to establish a private debug session may be carried out by receiving one or more application-level messages having a COMMAND request message type and a payload that includes a private debug session establishment command executable by the back-end debugger.

In the method of FIG. 10, routing (316) the application-level messages is carried out by forwarding (1004), to the back-end debugger, the request to establish a private debug session of the debuggee and returning (320) client-specific debug results including establishing (1006) the private debug session of the debuggee for the requesting debug client.

For further explanation, FIG. 11 sets forth a flowchart illustrating a further exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention. The method of FIG. 11 is similar to the method of FIG. 10 including as it does: receiving (1002), from a requesting debug client, a request to establish a private debug session of the debuggee; forwarding (1004), to the back-end debugger, the request to establish a private debug session of the debuggee; and establishing (1006) the private debug session of the debuggee for the requesting debug client.

In establishing the private debug session, method steps are carried out on the parent side (original instance of the back-end debugger and debuggee) and on the child side (private instance of the back-end debugger and debuggee). FIG. 11 is directed primarily to child side processing during establishment of the private debug session. Parent side processing during establishment of the private debug session will be addressed below with reference to FIG. 12.

In the method of FIG. 11, establishing (1006) the private debug session of the debuggee for the requesting debug client includes replacing (1102), by the back-end debugger at a stopped location in debuggee execution, original debuggee instructions with private debug session fork instructions. Replacing (1102) original debuggee instructions with private debug session fork instructions may be carried out in a manner similar to the insertion of breakpoints by a debugger in which machine instructions are replaced by instructions or one or more opcodes configured to stop execution of the debuggee. Here, rather than a breakpoint, the debugger replaces a set of original instructions with a set of predefined instructions—the private debug session fork instructions—and the original instructions may be stored for later use. Consider the following example source code, depicted here as C-type pseudocode rather than machine instructions for purposes of explanation:

write_routine( char *name ){   char n[1000];   char open_n[1000];   char cmd[1000];   FILE *out;   int i;   strcpy( n, name );   sprintf( open_n, “%s.c”, name ); //stopped location   build_it( open_n );   if ( foo(name )){   sprintf( cmd, “cat ../mods/%s.c > %s.c”, name, name );   } }

In the above pseudo-code, the comment “stopped location” indicates a location in code at which execution of debuggee is currently. In accordance with method of FIG. 11, the back-end debugger may replace a portion of the above code with private debug session fork instructions as follows:

write_routine( char *name ){   char n[1000];   char open_n[1000];   char cmd[1000];   FILE *out;   int i;   strcpy( n, name );   stopped_loc temp=fork( ); //begin private debug session   fork instructions   if ( temp==0 )   {     while ( !temp );     goto stopped_loc;   }   else   {     <BREAKPOINT OP CODE>     goto stopped_loc;   }//end private debug session fork instructions   if ( foo(name )){   sprintf( cmd, “cat ../mods/%s.c > %s.c”, name, name );   } }

In the pseudo-code above, the private debug session fork instructions begin at the line of code that includes the comment “begin private debug session fork instructions” and end at the line of code that includes the comment “end private debug session fork instructions.”

Establishing (1006) the private debug session in the method of FIG. 11 also includes executing (1104) the private debug session fork instructions of the debuggee. In the method of FIG. 11, executing (1104) the private debug session fork instructions of the debuggee is carried out by instantiating (1106) a private instance of the debuggee and waiting (1108), by the private instance of the debuggee, in a loop. Continuing with the example pseudo-code above, the back-end debugger begins execution from the stopped location, which executes a fork system call. A ‘fork’ system call effects a copy of a process calling the fork. The copy of the process is referred to as the “child” and the calling process from which the child is created is called the “parent.” The return of the fork system call indicates whether the process is the parent or child. The child, in the above example, is the debuggee of the private debug session and the parent is the original debuggee of the collaborative debug session. In the above example pseudo-code, the child receives an indication that it is the child, and waits in the “while” loop, “while (!temp).”

Establishing (1006) the private debug session in the method of FIG. 11 also includes receiving (1110), by the back-end debugger, a fork notification that includes an identifier of the private instance of the debuggee. The back-end debugger, having control of the collaborative session debuggee, may be registered with the operating system to receive an indication of forks carried out during debuggee execution.

Establishing (1006) the private debug session also includes forking (1112), by the back-end debugger, into a private instance of the back-end debugger and attaching, in dependence upon the identifier, the private instance of the debuggee in a private debug session. Once the collaborative session back-end debugger confirms the fork of the debuggee, the back-end debugger also forks. The child, or private session, back-end debugger then attaches to the child, or private session, debuggee in the same manner a debugger normally attaches to a debuggee. One example manner of attaching to the private instance of the debuggee is through the use of a ‘ptrace’ style system call. Once attached, the private instance of the back-end debugger may then stop execution of the private instance of the debuggee.

In the method of FIG. 11, establishing (1006) the private debug session also includes inserting (1114), by the private instance of the back-end debugger at the stopped location in the private instance of the debuggee, a breakpoint. Continuing with the above example pseudo-code the private instance of the debuggee is executing in the “while” loop and the private instance of the back-end debugger may insert a breakpoint as follows:

write_routine( char *name ){   char n[1000];   char open_n[1000];   char cmd[1000];   FILE *out;   int i;   strcpy( n, name );   stopped_loc: <BREAKPOINT OP CODE>//begin private   debug session fork instructions   if ( temp==0 )   {     while ( !temp );     goto stopped_loc;   }   else   {     <BREAKPOINT OP CODE>     goto stopped_loc;   }//end private debug session fork instructions   if ( foo(name )){   sprintf( cmd, “cat ../mods/%s.c > %s.c”, name, name );   } }

In the above example pseudo-code, the private instance of the back-end debugger has replaced the fork call from the private debug session fork instructions with a breakpoint opcode.

As mentioned above, a forked process—the child process—is a copy of the parent process. Breakpoints and other events established during the debug session of the debuggee then will also be copied to the private instance of the debuggee. To that end, the method of FIG. 11 also includes and optional step: removing (1116), by the private instance of the back-end debugger, from the private instance of the debuggee, events established by debug clients other than the requesting debug client.

Once the breakpoint is inserted (1114) the stopped location and any events established by other debug clients are removed (in embodiments in which the private instance of the back-end debugger is configured to do so), the method of FIG. 11 continues by releasing (1118), by the private instance of the back-end debugger, the private instance of the debuggee from the loop. Continuing with the above example pseudo-code, the private instance of the back-end debugger may release (1118) the private instance of the debuggee from the loop by setting the value of “temp” to one and stepping or initiating execution of the private debuggee.

Responsive to the release, the method of FIG. 11 continues by returning (1120), by the private instance of the debuggee, to the stopped location. In the example pseudo-code above, once the private debuggee exits the “while” loop, execution jumps, via a “goto” instruction, to the stopped location represented by “stopped loc.”

Once the private instance of the debuggee returns to the stopped location, the private instance of the debuggee in the method of FIG. 11 encounters (1122) the breakpoint, thereby stopping execution of the private instance of the debuggee. At this point, execution of the debuggee has returned to original stopped location.

The private instance of the back-end debugger in the method of FIG. 11 then replaces the original debuggee instructions at the stopped location and instantiates (1126) data communications with a graphical user interface (‘GUI’) of the requesting debug client. Instantiating data communications with a graphical user interface (‘GUI’) of the requesting debug client may be carried out through use of protocols supported by a listening agent, such as the agent (129) in the example of FIG. 1.

As mentioned above, FIG. 11 is directed primarily to operations carried out on the child side or private instance of the debuggee in establishing the private debug sessions. Such operations—on the parent and child side—may be carried out in parallel or nearly in parallel. For further explanation, FIG. 12 sets forth a flowchart illustrating a further exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention, directed primarily to operations on the parent side or collaborative debuggee during establishment (1006) of the private debug session.

The method of FIG. 12 includes many of the same elements as those found in FIG. 11. Establishing (1006) the private debug session in the method of FIG. 12, however, includes replacing (1202), at a stopped location in debuggee execution, original debuggee instructions with private debug session fork instructions, the private debug session fork instructions including a breakpoint to be encountered by the debuggee upon a fork. Continuing with the same example pseudo-code listed above with reference to FIG. 12, also including a comment to indicate the breakpoint to be encountered by the debuggee upon a fork:

write_routine( char *name ){   char n[1000];   char open_n[1000];   char cmd[1000];   FILE *out;   int i;   strcpy( n, name );   stopped_loc temp=fork( ); //begin private debug session   fork instructions   if ( temp==0 )   {     while ( !temp );     goto stopped_loc;   }   else   {     <BREAKPOINT OP CODE> //Parent encounters this breakpoint     goto stopped_loc;   }//end private debug session fork instructions   if ( foo(name )){   sprintf( cmd, “cat ../mods/%s.c > %s.c”, name, name );   } }

In the above, pseudo-code, private debug session fork instructions have replaced original instructions and a breakpoint to be encountered by the debuggee has been inserted as well. The breakpoint is included in the line of code indicated by the comment “Parent encounters this breakpoint.”

Establishing (1006) the private debug session in the example of FIG. 12 also includes executing (1204) the private debug session fork instructions of the debuggee and encountering (1206), by the debuggee, the breakpoint thereby stopping execution of the debuggee.

Once the debuggee of the collaborative debug session encounters the breakpoint and stops execution, the back-end debugger in the example of FIG. 12 replaces (1208) the breakpoint with one or more instructions to return the debuggee to the stopped location and inserts (1210) a breakpoint at the stopped location. Continuing with the above example pseudo-code, the back-end debugger may insert instructions to return the debuggee to the stopped location and insert a breakpoint at the stopped location as follows:

write_routine( char *name ){   char n[1000];   char open_n[1000];   char cmd[1000];   FILE *out;   int i;   strcpy( n, name );   stopped_loc: <BREAKPOINT OP CODE>//begin private   debug session fork instructions   if ( temp==0 )   {     while ( !temp );     goto stopped_loc;   }   else   {     temp = temp; //replace breakpoint with no-op     goto stopped_loc;   }//end private debug session fork instructions   if ( foo(name )){   sprintf( cmd, “cat ../mods/%s.c > %s.c”, name, name );   } }

In the above example pseudo-code the fork instruction of the private debug session has been replaced with a breakpoint and the breakpoint at which execution of the debuggee is currently stopped has been replaced with a meaningless instruction or a “no-op.” In this example, the no-op is depicted as “temp=temp.”

Once the breakpoint has been inserted at the stopped location and instructions to return the debuggee to the stopped location have been inserted, the method of FIG. 12 continues by resuming (1212) debuggee execution, returning (1214), by the debuggee, to the stopped location, and encountering (1216) the breakpoint thereby stopping execution of the debuggee. Once execution of the debuggee is stopped, the method of FIG. 12 continues by replacing (1218), by the back-end debugger, the original debuggee instructions at the stopped location.

As mentioned above, parent and child side operations carried out during the establishment of the private debug session may be carried out in parallel. To that end, the methods of FIG. 11 and FIG. 12 may be thought of as being execution in parallel. At the outset of establishing the private debug session, one debuggee and one debugger exist, the debuggee forks into parent and child, the debugger also forks into parent and child, and at the end of FIGS. 11 and 12, a collaborative debug session exists in which the parent debuggee is stopped at a particular location in code and a private debug session exists in which the child debuggee is stopped at the same location in a copy of the same code.

For further explanation, FIG. 13 sets forth a flowchart illustrating a further exemplary method of collaborative software debugging in a distributed system in accordance with embodiments of the present invention. FIG. 13 is similar to the method of FIG. 10, including many similar elements. In the method of FIG. 13, however, establishing (1006) the private debug session includes establishing (1302), in a GUI of the requesting debug client, a graphical representation of the private debug session in a new tab of the GUI or establishing (1304) a new window of a GUI of the requesting debug client, the new window setting forth a graphical representation of the private debug session.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable transmission medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable transmission medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable transmission medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart, block diagrams, and sequence diagrams, in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

It will be understood from the foregoing description that modifications and changes may be made in various embodiments of the present invention without departing from its true spirit. The descriptions in this specification are for purposes of illustration only and are not to be construed in a limiting sense. The scope of the present invention is limited only by the language of the following claims. 

1. A method of collaborative software debugging in a distributed system, the distributed system comprising a debug server, a plurality of debug clients, and a data communications network, the debug server coupled for data communications to the plurality of debug clients through the data communications network, the debug server comprising a debug administrator, a message router, a back-end debugger, and a debuggee, the method comprising: receiving, by the debug server from the debug clients asynchronously during a debug session of the debuggee, a plurality of application-level messages, including receiving, from a requesting debug client, a request to establish a private debug session of the debuggee; routing, by the message router in accordance with an application-level message passing protocol, the application-level messages among the debug clients, the debug administrator, and the back-end debugger, thereby providing distributed control of the back-end debugger to the debug clients with application-level messages routed to the back-end debugger, including forwarding, to the back-end debugger, the request to establish a private debug session of the debuggee; and returning, by the debug server to the debug clients in response to the application-level messages routed to the back-end debugger, client-specific debug results, including establishing the private debug session of the debuggee for the requesting debug client.
 2. The method of claim 1 wherein establishing the private debug session further comprises: replacing, by the back-end debugger at a stopped location in debuggee execution, original debuggee instructions with private debug session fork instructions; executing the private debug session fork instructions of the debuggee including: instantiating a private instance of the debuggee; and waiting, by the private instance of the debuggee, in a loop; receiving, by the back-end debugger, a fork notification that includes an identifier of the private instance of the debuggee; forking, by the back-end debugger, into a private instance of the back-end debugger, including attaching, in dependence upon the identifier, the private instance of the debuggee in a private debug session; inserting, by the private instance of the back-end debugger at the stopped location in the private instance of the debuggee, a breakpoint; releasing, by the private instance of the back-end debugger, the private instance of the debuggee from the loop; responsive to the release, returning, by the private instance of the debuggee, to the stopped location; encountering, by the private instance of the debuggee, the breakpoint, thereby stopping execution of the private instance of the debuggee; replacing, by the private instance of the back-end debugger, the original debuggee instructions at the stopped location; and instantiating, by the private instance of the back-end debugger, with a graphical user interface (‘GUI’) of the requesting debug client, data communications.
 3. The method of claim 2 further comprising removing, by the private instance of the back-end debugger, from the private instance of the debuggee, events established by debug clients other than the requesting debug client.
 4. The method of claim 1 wherein establishing the private debug session further comprises: replacing, at a stopped location in debuggee execution, original debuggee instructions with private debug session fork instructions, the private debug session fork instructions including a breakpoint to be encountered by the debuggee upon a fork; executing the private debug session fork instructions of the debuggee including encountering, by the debuggee, the breakpoint thereby stopping execution of the debuggee; replacing, by the back-end debugger, the breakpoint with one or more instructions to return the debuggee to the stopped location; inserting, by the back-end debugger at the stopped location, a breakpoint; resuming, by the back-end debugger, debuggee execution; returning, by the debuggee, to the stopped location; encountering the breakpoint thereby stopping execution; and replacing, by the back-end debugger, the original debuggee instructions at the stopped location.
 5. The method of claim 1 wherein establishing, the private debug session of the debuggee for the requesting debug client further comprises establishing, in a graphical user interface (‘GUI’) of the requesting debug client, a graphical representation of the private debug session in a new tab of the GUI.
 6. The method of claim 1 wherein establishing, the private debug session of the debuggee for the requesting debug client further comprises establishing a new window of a graphical user interface (‘GUI’) of the requesting debug client, the new window comprising a graphical representation of the private debug session.
 7. An apparatus for collaborative software debugging in a distributed system, the distributed system comprising a debug server, a plurality of debug clients, and a data communications network, the debug server coupled for data communications to the plurality of debug clients through the data communications network, the debug server comprising a debug administrator, a message router, a back-end debugger, and a debuggee, the apparatus comprising a computer processor, a computer memory operatively coupled to the computer processor, the computer memory having disposed within it computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of: receiving, by the debug server from the debug clients asynchronously during a debug session of the debuggee, a plurality of application-level messages, including receiving, from a requesting debug client, a request to establish a private debug session of the debuggee; routing, by the message router in accordance with an application-level message passing protocol, the application-level messages among the debug clients, the debug administrator, and the back-end debugger, thereby providing distributed control of the back-end debugger to the debug clients with application-level messages routed to the back-end debugger, including forwarding, to the back-end debugger, the request to establish a private debug session of the debuggee; and returning, by the debug server to the debug clients in response to the application-level messages routed to the back-end debugger, client-specific debug results, including establishing the private debug session of the debuggee for the requesting debug client.
 8. The apparatus of claim 7 wherein establishing the private debug session further comprises: replacing, by the back-end debugger at a stopped location in debuggee execution, original debuggee instructions with private debug session fork instructions; executing the private debug session fork instructions of the debuggee including: instantiating a private instance of the debuggee; and waiting, by the private instance of the debuggee, in a loop; receiving, by the back-end debugger, a fork notification that includes an identifier of the private instance of the debuggee; forking, by the back-end debugger, into a private instance of the back-end debugger, including attaching, in dependence upon the identifier, the private instance of the debuggee in a private debug session; inserting, by the private instance of the back-end debugger at the stopped location in the private instance of the debuggee, a breakpoint; releasing, by the private instance of the back-end debugger, the private instance of the debuggee from the loop; responsive to the release, returning, by the private instance of the debuggee, to the stopped location; encountering, by the private instance of the debuggee, the breakpoint, thereby stopping execution of the private instance of the debuggee; replacing, by the private instance of the back-end debugger, the original debuggee instructions at the stopped location; and instantiating, by the private instance of the back-end debugger, with a graphical user interface (‘GUI’) of the requesting debug client, data communications.
 9. The apparatus of claim 8 further comprising computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the step of removing, by the private instance of the back-end debugger, from the private instance of the debuggee, events established by debug clients other than the requesting debug client.
 10. The apparatus of claim 7 wherein establishing the private debug session further comprises: replacing, at a stopped location in debuggee execution, original debuggee instructions with private debug session fork instructions, the private debug session fork instructions including a breakpoint to be encountered by the debuggee upon a fork; executing the private debug session fork instructions of the debuggee including encountering, by the debuggee, the breakpoint thereby stopping execution of the debuggee; replacing, by the back-end debugger, the breakpoint with one or more instructions to return the debuggee to the stopped location; inserting, by the back-end debugger at the stopped location, a breakpoint; resuming, by the back-end debugger, debuggee execution; returning, by the debuggee, to the stopped location; encountering the breakpoint thereby stopping execution; and replacing, by the back-end debugger, the original debuggee instructions at the stopped location.
 11. The apparatus of claim 7 wherein establishing, the private debug session of the debuggee for the requesting debug client further comprises establishing, in a graphical user interface (‘GUI’) of the requesting debug client, a graphical representation of the private debug session in a new tab of the GUI.
 12. The apparatus of claim 7 wherein establishing, the private debug session of the debuggee for the requesting debug client further comprises establishing a new window of a graphical user interface (‘GUI’) of the requesting debug client, the new window comprising a graphical representation of the private debug session.
 13. A computer program product for collaborative software debugging in a distributed system, the distributed system comprising a debug server, a plurality of debug clients, and a data communications network, the debug server coupled for data communications to the plurality of debug clients through the data communications network, the debug server comprising a debug administrator, a message router, a back-end debugger, and a debuggee, the computer program product disposed upon a computer readable medium, the computer program product comprising computer program instructions that, when executed by a computer processor of a computer, cause the computer to carry out the steps of: receiving, by the debug server from the debug clients asynchronously during a debug session of the debuggee, a plurality of application-level messages, including receiving, from a requesting debug client, a request to establish a private debug session of the debuggee; routing, by the message router in accordance with an application-level message passing protocol, the application-level messages among the debug clients, the debug administrator, and the back-end debugger, thereby providing distributed control of the back-end debugger to the debug clients with application-level messages routed to the back-end debugger, including forwarding, to the back-end debugger, the request to establish a private debug session of the debuggee; and returning, by the debug server to the debug clients in response to the application-level messages routed to the back-end debugger, client-specific debug results, including establishing the private debug session of the debuggee for the requesting debug client.
 14. The computer program product of claim 13 wherein establishing the private debug session further comprises: replacing, by the back-end debugger at a stopped location in debuggee execution, original debuggee instructions with private debug session fork instructions; executing the private debug session fork instructions of the debuggee including: instantiating a private instance of the debuggee; and waiting, by the private instance of the debuggee, in a loop; receiving, by the back-end debugger, a fork notification that includes an identifier of the private instance of the debuggee; forking, by the back-end debugger, into a private instance of the back-end debugger, including attaching, in dependence upon the identifier, the private instance of the debuggee in a private debug session; inserting, by the private instance of the back-end debugger at the stopped location in the private instance of the debuggee, a breakpoint; releasing, by the private instance of the back-end debugger, the private instance of the debuggee from the loop; responsive to the release, returning, by the private instance of the debuggee, to the stopped location; encountering, by the private instance of the debuggee, the breakpoint, thereby stopping execution of the private instance of the debuggee; replacing, by the private instance of the back-end debugger, the original debuggee instructions at the stopped location; and instantiating, by the private instance of the back-end debugger, with a graphical user interface (‘GUI’) of the requesting debug client, data communications.
 15. The computer program product of claim 13 further comprising computer program instructions that, when executed by a computer processor of a computer, cause the computer to carry out the step of removing, by the private instance of the back-end debugger, from the private instance of the debuggee, events established by debug clients other than the requesting debug client.
 16. The computer program product of claim 13 wherein establishing the private debug session further comprises: replacing, at a stopped location in debuggee execution, original debuggee instructions with private debug session fork instructions, the private debug session fork instructions including a breakpoint to be encountered by the debuggee upon a fork; executing the private debug session fork instructions of the debuggee including encountering, by the debuggee, the breakpoint thereby stopping execution of the debuggee; replacing, by the back-end debugger, the breakpoint with one or more instructions to return the debuggee to the stopped location; inserting, by the back-end debugger at the stopped location, a breakpoint; resuming, by the back-end debugger, debuggee execution; returning, by the debuggee, to the stopped location; encountering the breakpoint thereby stopping execution; and replacing, by the back-end debugger, the original debuggee instructions at the stopped location.
 17. The computer program product of claim 13 wherein establishing, the private debug session of the debuggee for the requesting debug client further comprises establishing, in a graphical user interface (‘GUI’) of the requesting debug client, a graphical representation of the private debug session in a new tab of the GUI.
 18. The computer program product of claim 13 wherein establishing, the private debug session of the debuggee for the requesting debug client further comprises establishing a new window of a graphical user interface (‘GUI’) of the requesting debug client, the new window comprising a graphical representation of the private debug session.
 19. The computer program product of claim 13 wherein the computer readable medium comprises a storage medium.
 20. The computer program product of claim 13 wherein the computer readable medium comprises a transmission medium. 